Network elements are components used in communications networks. A common type of network element is a switch. A switch routes data from a plurality of data input paths to a variety of data output paths dependent on the destination of the data.
Network elements are often physically constructed in units referred to as “shelves.” A shelf typically comprises a main housing provided with a power supply system, an environmental control (i.e. cooling) system, user controls, information displays, and a main circuit board, called a “backplane” or a “midplane.” The backplane or midplane provides a number of slots or sockets to which circuit components or “cards” can be mounted. A “backplane” circuit board typically has card slots on only one of its surfaces. A “midplane” typically has card slots on both sides. The “backplane” or “midplane” is typically mounted in the housing so that cards can be inserted or removed from the outside. The circuit board provides one or more communications busses and other electrical connections to which each card is electrically connected when inserted in a slot or socket. A backplane can be very complex, containing a dozen or more slots on each surface and hundreds of interconnections between and among the slots.
Types of cards used in switches include line processing cards, intershelf communications cards, and control cards. The majority of cards in a network element are commonly line processing cards, which provide the data path functionality for the network element. One and often two (for redundancy) slots are sometimes populated with control cards that provide control, accounting and management functions for the line processing cards.
Although prior art shelves provide some flexibility by allowing different cards providing different kinds of data path functionality to be plugged into the backplane or midplane slots, that flexibility is limited because the circuit cards used must be compatible with the parameters of the particular slot configuration provided by the backplane/midplane. Prior art network element shelves cannot be used with cards that have new or different configurations and that provide new or improved data path functionality. To utilize new card configurations and capacities, a completely new shelf, including a new backplane or midplane, must be designed. As a result, the process of upgrading to new features and capabilities is time consuming and expensive for manufacturers and users.